The protection of rubber vulcanizates from destructive environmental influences by means of anti-aging agents is known. Thus e.g. phenolic, aminic, sulfur-containing or phosphor-containing anti-aging agents are added to rubber vulcanizates to improve their heat-resistance and storage stability. An overview of known anti-aging agents for rubbers is disclosed, for example, in Ullmanns Enzyklopädie der technischen Chemie, Verlag Chemie, Weinheim, 4th edition (1974), volume 8, pp. 19-45.
Improved, co-vulcanizable anti-aging agents, which can be produced by reacting optionally substituted p-phenylenediamines and/or sterically hindered phenols with bifunctional alkyl-, aryl- and/or aralkyl compounds and subsequently reacting the product thus obtained with sulfur and/or sulfur-yielding compounds, are disclosed in co-pending U.S. patent application Ser. No. 09/850,511.
Co-pending U.S. patent application Ser. No. 09/850,511 discloses known anti-aging agents for rubber vulcanizates, although it should be pointed out that the known anti-aging agents have considerable disadvantages because of their ready volatility or extractability. The co-vulcanizable anti-aging agents disclosed in co-pending U.S. patent application Ser. No. 09/850,511 avoid these disadvantages.
However, to produce the anti-aging agents disclosed therein, a relatively complex, two-stage synthesis is required, which comprises the reaction of, for example, phenylenediamines with difunctional alkyl-, aryl- or aralkyl compounds with subsequent reaction of the products obtained in this reaction with sulfur and/or sulfur-yielding compounds.
An object of the present invention is therefore to provide an anti-aging agent that can be produced in a simple, single-stage synthesis and avoids the disadvantages of the known anti-aging agents already mentioned in co-pending U.S. patent application Ser. No. 09/850,511, such as volatility and extractability, without reducing the effectiveness of the anti-aging agent according to the present invention in comparison with the anti-aging agents previously known.